A-Level Environmental Science: Soil Fertility and Management

Practice flashcards covering the physical environment, soil fertility, human impacts on soil, erosion mechanics, and soil sampling techniques/experiments for A-Level Environmental Science.

How is soil fertility defined in Environmental Science?

The soil's ability to support the growth of crops to ensure a high yield and productivity.

What are the three components that define soil texture?

The proportions of sand, silt, and clay in the soil.

Why do clay soils tend to have lower and less fluctuating temperatures than sandy soils?

Clay soils retain a high volume of water, and because water has a high specific heat capacity, it requires significant energy to alter its temperature.

What is the difference between soil texture and soil structure?

Soil texture is the proportion of sand, silt, and clay; soil structure is the way in which soil particles clump together to form aggregates called peds.

Describe the characteristics of crumb peds versus platy peds.

Crumb peds are round and small, allowing for high aeration, drainage, and root penetration. Platy peds are long and flat, reducing aeration and drainage while making root penetration difficult.

What is the ideal pH range for fertile soil, and why?

Between $5.5$ and $7$, as this sits within the range of tolerance for many plant and soil biota species.

How does overly acidic soil affect nutrient availability?

It increases the solubility of nutrients like nitrates and phosphates, making them more likely to leach from the soil, and can damage root hair membranes.

What are the two main groups of fertilizers used in agriculture?

Organic (natural sources like manure) and inorganic (artificial chemicals made using the Haber process).

What is 'green manure'?

Crops grown alongside commercial crops specifically to be ploughed back into the soil to increase organic matter.

What is the risk of over-ploughing soil?

It can lead to the breakdown of soil structure (peds), leading to reduced aeration and fertility.

How does 'zero-tillage' farming improve sustainability?

It involves not ploughing or disrupting the soil structure, which ensures humus levels remain stable and prevents the breakdown of peds.

Define soil erosion.

A natural process where wind or water removes soil particles.

What is the difference between 'erodibility' and 'erosivity'?

Erodibility is a measure of how susceptible the soil is to erosion; erosivity is the kinetic energy required to separate and remove soil particles.

Describe 'rain splash erosion'.

The splash of a raindrop onto the soil dislodges soil particles; the effect is worsened by heavier rain.

What is 'contour ploughing'?

Ploughing at a $90$-degree angle to the slope to create furrows that slow down water movement and reduce its kinetic energy.

What is the formula for the Universal Soil Loss Equation (USLE)?

$$A = R \times K \times L \times S \times C \times P$$

In the USLE formula, what do the variables 'R' and 'S' represent?

$R$ is the rainfall erosivity factor; $S$ is the slope gradient factor.

According to USLE categories, what is the rate of soil loss for 'High' erodibility?

$20$-$30\,t/ha/yr^{-1}$

What is the recommended minimum number of soil samples for a study area to ensure representative data?

$10$ samples.

How can a soil auger be used to standardize soil collection?

It can be pushed into the ground to a standardized depth to collect a consistent volume of soil each time.

Describe the sedimentation method for determining soil texture.

Soil is placed in a tube with water and shaken; particles are allowed to settle for several days and are measured as layers (sand settles first, then silt, then clay).

Why is soil heated to $100\,^{\circ}C$ for at least $24$ hours when testing for water content?

$100\,^{\circ}C$ is the boiling point of water, ensuring it evaporates; the soil is re-weighed until it reaches a constant mass.

What is the temperature range used to burn off soil organic matter, and why is this range chosen?

Between $200\,^{\circ}C$ and $500\,^{\circ}C$; this is high enough to burn off organic matter but not so high that it breaks down soil minerals.

How is bulk density calculated?

$\frac{\text{weight of dry soil}}{\text{Volume of soil}}$ (typically measured in $g/cm^3$ or $kg/cm^3$).

Describe the function of a Tullgren funnel.

It uses a light source to act as an irritant to soil organisms, driving them downward through a funnel and into a collection chamber.

What is a 'pooter'?

A sampling device used to pick up small invertebrates by sucking on one pipe to draw the organism into a clear jar, with gauze preventing ingestion.